Screed extension assembly for asphalt paving machines

ABSTRACT

Segmental extension units which interlock to provide selected extension of the screed of an asphalt paving machine are disclosed. Each extension unit has a forward end incorporating locking rings adapted to mate with studs in the trailing end of a preceding extension unit. The locking rings are disposed about cam surfaces so that upon rotation of locking handles two adjacent extension units will be rigidly interconnected. Adjustment members permit adjustment of the relative positions of adjacent lower surfaces of the extension members to accommodate wear of the assemblies and to permit the use of forward and trailing edges of the screed extensions as screed surfaces. Construction details of preferred embodiments are disclosed.

United States atent Birtchet 1 July 4,1972

[54] SCREED EXTENSION ASSEMBLY FOR ASPHALT PAVING MACHINES [72] Inventor: Ralph D. Birtchet, Galvin, Wash.

[73] Assignee: Schneider-Simpson, lnc., Tacoma, Wash.

[22] Filed: June 15, 1970 [21] Appl. No.: 46,309

3,251,281 5/1966 lanetti ..94/45 Primary ExaminerJacob l. Nackenoff Attorney-Christensen and Sanborn 57 ABSTRACT Segmental extension units which interlock to provide selected extension of the screed of an asphalt paving machine are dis closed. Each extension unit has a forward end incorporating locking rings adapted to mate with studs in the trailing end ofa preceding extension unit. The locking rings are disposed about cam surfaces so that upon rotation of locking handles two adjacent extension units will be rigidly interconnected. Adjustment members permit adjustment of the relative positions of adjacent lower surfaces of the extension members to accommodate wear of the assemblies and to permit the use of forward and trailing edges of the screed extensions as screed surfaces. Construction details of preferred embodiments are disclosed.

13 Claims, 5 Drawing Figures PATENTEDJUL 4 m2 SHEET 10F 2 INVENTOR. F411 & B/FTCHET SCREED EXTENSION ASSEMBLY FOR ASPHALT PAVING MACHINES Asphalt paving machines are in common use throughout the road construction industry. Such machines typically include an initial leveling surface referred to as a screed for leveling the bituminous material which is then compacted while the material is at an elevated temperature. The asphalt laying machine itself is typically a heavy and slow-moving piece of machinery and therefore is usually trucked to the construction site on a given highway. Due to the load width limitations on many highways the asphalt paving machine is typically constructed to a width which is less than the desired width of a given strip of asphalt to be layed. Thus various types of extension units are required in order to extend the screed surface to the full width desired for a given operation. By constructing the asphalt paving machine to a width corresponding to the minimum width of a road project and then adding extension units of varying length it will be seen that a given paving machine can be adjusted on location to lay a strip of asphalt material to anydesired dimension.

A problem has existed in the art in connection with extending the width of the screed assembly in that it typically takes several hours to perform the screed extension operation. In some assemblies the services of a welder are required while in other cases an extensive mechanical modification necessitates the presence of skilled mechanics to perform the desired screed extension operation. Such screed extension units known to the art are also not reversible in the sense that once the lower surface of the screed extension unit has been worn due to usage the lower surface must either be resurfaced or the extension unit discarded.

It is therefore an object of the present invention to provide an improved screed extension assembly for an asphalt paving machine. Another object of the present invention is to provide a unitized screed extension system utilizing interconnected screed extension units to obtain a total screed extension of a selected dimension.

Another object of the present invention is to provide an improved locking assembly for interconnecting screed extension units. I

- A further object of the present invention is to provide screed extension assemblies having an enclosed interior adapted to receive hot gases for maintaining the screed extension assembly and hence the asphalt material therebeneath at an elevated temperature.

Another object of the present invention is to provide screed extension units having means for adjusting the relative elevation of adjacent asphalt-engaging surfaces.

Another object of the present invention is to provide screed extension units having forward and trailing edges adapted for a screeding operation to thereby permit extended life of the extension unit due to the reversible nature of the screed extension unit.

In accordance with the teachings of the present invention the screed extension units have the general configuration of channel-like steel assemblies having a rectangular cross section and a hollow interior. Thus the assembly resembles an open-ended right rectangular parallelogram similar to an open-ended rectangular box. In one end of the extension unit four heavy studs extend toward the longitudinal axis of the assembly with two of the studs extending from the upper surface and two extending from the lower surface. The opposite end of the extension unit is provided with four steel coupling rings each of which is adapted to be disposed about one of the studs in a preceding extension unit. The coupling rings are disposed respectively about cam surfaces carried by a pair of lock shafts which extend through the interior of the extension unit and are provided with handles to permit rotation thereof from outside the extension unit. The arrangement is such that when the cam surfaces are rotated the steel rings serve to pull the succeeding extension assembly into tight engagement with a preceding extension unit and thus a rigid interconnection results.

To permit rapid assembly of the extension units even though they are made of heavy weight material each extension unit is provided with a pair of longitudinal (or axial) studs extending parallel to the longitudinal axis of the extension unit and protruding beyond the open end thereof. Each of these two studs mates with an elongated slot in a plate extending perpendicular to the longitudinal axis of a preceding extension unit so that the user can insert the axial studs in the elongated slots during initial coupling of the extension assemblies. A small plate member is hinged to the top surface of each extension unit and is provided with an opening therein. Each extension unit also has a vertical stud on the exterior of the top surface along the trailing end so that said opening in the hingedly connected member can be disposed about said stud and provide a temporary coupling between adjacent extension assemblies.

By constructing the screed extension units in the manner above described it is found that both the trailing and leading edges of the extension units can be used as a leading screed surface simply by using a given screed extension unit on an opposite side of the asphalt paving machine once one of the surfaces has become worn. To accommodate elevational differences in the lower asphalt-engaging surfaces due to wear of the surfaces through usage each of the extension assemblies is provided with locking adjustment members.

The above and additional advantages and objects of the invention will be more clearly understood from the following description when read with reference to the accompanying drawings.

FIG. 1 is a perspective view of a conventional asphalt paving machine having three screed extension units of the present invention secured to one side thereof.

FIG. 2 is a side elevation view with a section removed and showing a first pair of extension units interconnected with a third extension unit about to be coupled thereto.

FIG. 3 is a plan view of the apparatus of FIG. 2 with a section of the top plate of one unit cut away.

FIG. 4 is an end view of an extension unit as seen from the outer or tail end thereof.

FIG. 5 is a perspective view of one pair of the lower plate adjustment members on two adjacent extension units.

In FIG. 1 a conventional asphalt paving machine is shown generally at 10 with a truck 11 in the process of dumping mix 12 intothe hopper for spreading to form the road surface 13. The machine per se is well known in the art and is typified by those manufactured by the Barber-Greene Company and therefore a detailed explanation of the machine will not be included herein since the present invention relates to the extension units 15, 16, and 17 shown as connected to the slightly modified end of the machine screed assembly. The units l5, l6, and 17 are identical with the exception that the unit l5 has an end plate 18, secured thereto by bolts 19, 20, 21, and 22. The bolts 19-22 engage the threaded holes 19A, 20A, 21A, and 22A on the small plates across the trailing end of each unit (FIG. 4).

As best seen in FIGS. 2 and 4 each screed extension unit is composed of a lower channel member 30 and an upper channel member 31. The upper channel member 31 has offset lower sides seen at 31A and 318 so that the units can be interconnected and fonn an elongated channel member having a rectangular cross section and an open interior. As best seen in the end view of FIG. 4 and the plan view of FIG. 3, the upper channel member 31 is provided with four interior plates 31C which are welded thereto, and the lower member 30 is provided with four interior plates 30C which are welded thereto.

a The threaded studs 34 having the locknuts 34A disposed on opposite sides of the plates 30C and 31C pass through holes in the plates (or tabs). It will be seen that the nuts when tightened provide a means to rigidly interconnect the upper and lower channel members 31 and 30 to provide the main body of the extension unit.

As seen in FIGS. 1, 2 and 3 the extension units are adapted for interconnection to each other and thus for purpose of explanation the end adapted for connection to the asphalt paving machine will be referred to as the leading end while the opposite end will be referred to as the trailing end. As seen most clearly in FIGS. 2 and 4 the trailing end of each extension unit is provided with four heavy inwardly extending studs 41, 42, 43 and 44. Studs 41 and 42 are welded to and extend upwardly from the lower section 30 and the studs 43 and 44 are welded to and extend downwardly from the upper section 1 1. Each of these studs is adapted to be encompassed by one of the steel rings 51, 52, 53 and 54 located in the leading end of each extension unit. Note that rings 53 and 54 are longer than the lower rings 51 and 52. Each of these steel rings 51-54 has an outer end 51A-54A which is arcuate in shape and has a curvature such that it is adapted to mate with and uniformly engage a stud 41-44 of a preceding unit (see FIG. 3). Thus the inner radius of the outer ends 51A-54A corresponds to the radius of curvature of the studs 41-44. The inner ends SIB-54B have a larger radius of curvature and are adapted to mate with and are disposed about the circular surface of the associated cam member 61-64 secured to the control shafts 35 and 36. Handles 37 and 38 secured to the upper ends of the shafts 35 and 36 provide adjustment handles which upon rotation cause the cam surfaces 61-64 to be rotated and hence cause the coupling rings 31-34 to move inwardly or outwardly from the interior of the extension member depending upon the direction of rotation of the handles 37 and 38. It should be observed that the cam members 61-64 are actually circular in cross section but the shafts 35 and 36 are welded thereto in an otT-center position to achieve the cam action. It will be seen that cam members 63 and 64 have enlarged flanges 63A and 64A which prevent the associated ring 53-54 from falling away from the cam surface prior to the coupling operation.

It will be seen that each shaft 35-36 has welded beneath the associated handle 37-38 a small rectangular plate 37A-38A. Each of these two plates has a hole therein so that the locking pins 47 and 48 can drop through the holes and into one of the holes 49 in the upper surface of the extension member. These holes 49 are preferably threaded and hence bolts can be used as the pins 47 and 48 for locking the handles 37 and 38 in their respective rotated positions after the interconnection of adjacent extension units has been accomplished.

Each of the extension units has a pair of small plates 65 and 66 welded to the interior of the side surfaces near the leading end with each plate carrying an axially extending stud 67,68 which protrudes beyond the leading end of the extension unit. The studs 67-68 are adapted for engagement in the associated opening 69-70 of the plates 71,72 located in the trailing end of a preceding extension unit. The arrangement is such that the studs 67 and 68 serve as initial guide members when inserted in the openings 69 and 70 during initial interconnection of the adjacent extension units.

In coupling one unit to a preceding unit the lower steel rings 51 and 52 are placed over the studs 41 and 42 of the preceding unit and the studs 67 and 68 are placed in the openings 69 and 70. The succeeding unit is then pushed against the preceding unit and temporarily connected thereto by the use of the hinged plate 74 welded to the top surface of the leading end of each extension unit. Each plate 74 is hinged at 75 and is provided with a hole 74A adapted to encompass the vertical stud 76 which extends upwardly from the top surface near the trailing end of each extension unit. Once this has been accomplished it will be seen that the adjacent extension units are temporarily interconnected and thus the person performing the interconnect operation is relieved of the strain associated with holding the relatively heavy extension unit while the coupling operation in completed.

As noted above, the lower coupling rings 51 and 52 are first positioned around studs 41 and 42 and the above-described temporary coupling takes place, the operator using the strap plate 74 and stud 75 to hold the parts together. The operator then reaches inside the extension unit being added to a preceding unit and positions the upper coupling rings 53 and 54 about the upper studs 43 and 44. It will be seen that the length of the cam surfaces 63 and 64 is sufficient to permit the ends 53A and 54A of rings 53 and 54 to be lowered (i.e. the rings placed at an angle with respect to the horizontal) and passed around the studs 43 and 44. While the upper rings 53 and 54 could be made of a size identical to the lower ring 51 and 52 with the upper studs 43 and 44 directly above studs 41 and 42, it has been found that displacing the studs 43 and 44 toward the center of the top (i.e. nonaligned with studs 41 and 42) the assembly function is made easier. As the rings are placed around the studs one at a time the associated handle 37 or 38 is rotated to a slight extent so that one set of coupling rings on one shaft 35 or 36 is held in position while the other set is aligned. Thus the coupling rings all are brought to an initial condition such that pressure between the studs 41-44 and the shafts 35 and 36 occurs. Any suitable lever such as a piece of pipe placed over the handles 37 and 38 can then be used to exert substantial pressure via the cams 61-64 to fimrly lock the adjacent extension assemblies together. The lock pins 47 and 48 are then dropped or threaded into position.

It will be observed that the lower front and lower rear edges of each extension unit are curved, as seen at 30F and 30R. The reason for this is that if one assumes that the edge 30F is initially used as the front of the screed surface it will be found that the bottom surface of the extension unit will gradually wear in a front-to-rear direction due to movement of the extension unit across the asphalt surface. Eventually the surface would wear to the point where repair or replacement would be required. With the units shown herein having two screed surfaces 30F and 30R extending up from the bottom surface the useful life of each extension unit is efiectively doubled in that a given extension unit can be removed from the lefi-hand side of a machine as illustrated in the drawings and connected to the right-hand side of the machine. Thus the rear surface 10R now becomes the front surface when positioned on the opposite side of the machine.

The extension unit for the machine should present a bottom surface which is coplanar with the screed surface being extended. When wear occurs as described above it will be seen that transfer of a given extension unit to the opposite side of the machine can result in a slight elevation diflerential between adjacent surfaces of the interconnected screed extension units. This would be the case when a worn unit on the left is removed and connected to a new extension unit on the right. Thus it would be advantageous to be able to bring the worn surface into alignment with the surface of an adjacent extension unit or the surface of an adjacent main screed surface. For this reason each of the screed extension units includes four adjustment devices 81, 82, 83, and 84 (FIGS. 3 and 4). The adjustment devices 81 and 82 are identical and are located near the edge of the trailing end, and devices 83 and 84 located near the leading end are identical. FIG. 5 shows the construction details most clearly. The device 84 is in the form of a heavy parallelogram of steel welded to the interior of the screed extension unit. The extended portion 84A overlies the bottom edge of a preceding unit. The bolt 85 threaded in nut 86 welded to the portion 84A passes through the portion 84A and engages the edge of the bottom of the adjacent extension unit. The device 82 located near the edge of the trailing end comprises a hollow rectangular body 87 welded to the bottom of the unit. A movable block 88 fits inside the body 87 and carries a bolt and nut assembly 89-90 similar to the bolt and nut assembly 85-86. The locking bolt 91 serves to lock block 88 in position, the arrangement being such that the block 88 can easily be removed or retracted inside body 87 when a given extension unit is the last one in an assembly and has an end plate 18 secured thereto (FIG. 1).

It will be seen in FIG. 5 that when the bolts 85 and 89 are adjusted they will serve to exert presure on the surface of the bottom portion of the adjacent screed extension unit and hence permit forcing the adjacent surfaces into exact alignment.

From the above it will be seen that a novel screed extension unit has been disclosed. As seen in FIG. 3 the end of the screed portion of a machine can be readily modified to have a set of studs corresponding to the studs 4144. While the four studs do all that is needed on the machine, it has been found convenient to in general duplicate the trailing end of an extension unit. In practice it is convenient to simply weld either a complete unit or the trailing end portion of a unit to the machine to serve as an anchor for the first extension unit. As seen in FIGS. 3 and 4 a reinforcing bar 95 can be welded to the inside of the top portion 31 to provide an added surface to which the upper studs 43 and 44 are welded. By having the units hollow hot gases for heating the asphalt can be circulated inside the units. It will of course be evident that units of varying length can be fabricated to permit the assembly of a plurality of standard units to achieve a desired length of screed extension.

What is claimed is:

1. An extension unit for the screed structure of an asphalt paving-machine comprising in combination: a body member including a substantially flat bottom plate, a top wall spaced apart from said bottom plate and first and second spacedapart side walls extending between said top wall and said bottom plate, said body member having a hollow interior defined by said bottom plate, top wall and side walls, and at least one open end; first and second spaced-apart, substantially vertical shafts extending across the interior of said body member adjacent said open end; means supporting said shafts for rotation about their respective longitudinal axes, said shafts being rotatable by their upper ends from the exterior of said body member; first cam means including a first eccentric secured to said first shaft and located inside said body member; second cam means including a second eccentric secured to said I second shaft and located inside said body member; first and second tensioning means respectively disposed about said first and second'eccentrics, said tensioning means extending outwardly from said open end of said body member and being adapted to be moved toward the interior of said body member when said eccentrics are rotated, whereby when said shafts are rotated, said tensioning means when coupled to another extension unit or to the screed structure of an asphalt paving machine will serve to pull said body member into engagement with said other unit or said screed structure.

2. The apparatus of claim 1 wherein said side walls and said bottom plate define two arcuate screed surfaces along opposite lower edges of the body member.

3. The apparatus of claim 1 wherein said body member has a second open end, and tensioning member attachment means secured to and disposed-inside of said body member adjacent said second open end.

4. The apparatus of claim 3 wherein said attachment means includes a plurality of stud means extending from the body member toward the interior thereof, and said tensioning means comprise a plurality of closed loop members adapted to be positioned about the stud means of another similar extension unit. I

5. The apparatus of claim 3 wherein said tensioning means comprise a plurality of closed loop members having first ends disposed about said cam means and second ends connectable to the tensioning member attachment means of another extension unit. 7

6. The apparatus of claim 4 wherein said body member includes a plate member pivotally secured to the exterior of said top wall near said first open end, and coupling means defined on said top wall near said second open end of said body member adapted for connection to the said plate member of another extension unit. I

7. The apparatus of claim 1 wherein the upper ends of said shafts extend through and terminate above said top wall.

8. An extension unit for the screed of an asphalt paving machine comprising in combination: a body member having a hollow interior, first and second open ends, and including a substantially flat bottom plate; first and second shafts extending across the interior of said body member adjacent said first open end and including means supporting said shafts for rotation; first cam means secured to said first shaft and located inside said body member; second cam means secured to said second shaft and located inside said body member; first and second tensioning means respectively disposed about said first and second cam means and extending outwardly from said first open end of said body member and adapted to be moved toward the interior of said body member when said cam means are rotated; tensioning member attachment means secured to and disposed inside said body member adjacent said second open end, said attachment means including a plurality of stud means extending from the body member toward the interior thereof, said tensioning means comprising a plurality of closed loop members adapted to be positioned about the stud means of another extension unit, said closed loop members being steel rings having first ends disposed about said cam means with a curvature matching said cam means and second ends with a curvature matching the curvature of said stud means, whereby said tensioning means when coupled to another extension unit or an asphalt paving machine will serve to pull said body member into engagement with said other unit or the machine.

9. An extension unit for the screed of an asphalt paving machine comprising in combination: a body member having a hollow interior, at least one open end, and including a substantially flat bottom plate; first and second shafts extending across the interior of said body member adjacent said open end and including means supporting said shafts for rotation; first cam means secured to said first shaft and located inside said body member; second cam means secured to said second shaft and located inside said body member; first and second tensioning means respectively disposed about said first and second cam means and extending outwardly from said open end of said body member and adapted to be moved toward the interior of said body member when said cam means are rotated; lock means coupled with said shafts for selectively locking said shaft against rotation when said tensioning means have been pulled to the innermost position thereof with respect to said body member, whereby said tensioning means when coupled to another extension unit or an asphalt paving machine will serve to pull said body member into engagement with said other unit or the machine.

10. An extension unit for the screed of an asphalt paving machine comprising in combination: a body member having a hollow interior, at least one open end, and including an upper and a lower member each having a substantially flat section respectively defining the top and bottom of the body member and each having side wall sections extending substantially perpendicular from the respective top and bottom of the body member and means interconnecting said upper and lower members to define said body member; first and second shafts extending across the interior of said body member adjacent said open end and including means supporting said shafts for rotation; first cam means secured to said first shaft and located inside said body member; second cam means secured to said second shaft and located inside said body member; first and second tensioning means respectively disposed about said first and second cam means and extending outwardly from said open end of said body member and adapted to be moved toward the interior of said body member when said cam means are rotated; a first plurality of stud means extending downwardly from said top of said body member; a second plurality of studs extending upwardly from said bottom of said body member; said tensioning means comprising elongated members having a first end coupled with said cam means and a second end connectable to the studs of another unit, whereby said tensioning means when coupled to another extension unit or an asphalt paving machine will serve to pull said body member into engagement with said other unit or machine.

11. The apparatus of claim 10 wherein said cam means comprises first and second substantially cylindrical cam members secured to said first shaft; third and fourth substantially cylindrical cam members secured to said second shaft; and said elongated members are each in the form of closed loop members having arcuate end sections.

12. A screed extension unit for an asphalt paving machine comprising an elongated body member having first and second open ends, a hollow interior, and a flat bottom; a plurality of stationary connection members secured to the walls of said body member near the first end thereof; a plurality of movable connection members; means supporting said movable connection members near said second open end and including means for extending and retracting said movable members in a direction parallel to the longitudinal axis of the body member, said means for extending and retracting comprising first and second shafts extending through the interior of the body member and each having a plurality of cam means secured thereto and engaged with said movable members and said movable members having means engageable with the stationary members of another extension unit to thereby interconnect two adjacent units and cause the same to be pulled together when said movable members are moved from their extended to their retracted positions; first and second bottom adjustment means secured to said flat bottom of said body member adjacent said first open end and each having an end portion extending beyond the edge of said first open end; first and second threaded members extending respectively through said end portions and perpendicular to said bottom; third and fourth bottom adjustment means secured to said flat bottom of said body member adjacent said second open end and each having an end portion extending beyond the edge of said second open end; and third and fourth threaded members extending respectively through said end portions of said third and fourth adjustment means and perpendicular to said bottom.

13. The apparatus of claim 12 wherein said end portion of said third and fourth adjustment means are retractable to positions completely inside said body member.

. i i t t 

1. An extension unit for the screed structure of an asphalt paving machine comprising in combination: a body member including a substantially flat bottom plate, a top wall spaced apart from said bottom plate and first and second spaced-apart side walls extending between said top wall and said bottom plate, said body member having a hollow interior defined by said bottom plate, top wall and side walls, and at least one open end; first and second spaced-apart, substantially vertical shafts extending across the interior of said body member adjacent said open end; means supporting said shafts for rotation about their respective longitudinal axes, said shafts being rotatable by their upper ends from the exterior of said body member; first cam means incLuding a first eccentric secured to said first shaft and located inside said body member; second cam means including a second eccentric secured to said second shaft and located inside said body member; first and second tensioning means respectively disposed about said first and second eccentrics, said tensioning means extending outwardly from said open end of said body member and being adapted to be moved toward the interior of said body member when said eccentrics are rotated, whereby when said shafts are rotated, said tensioning means when coupled to another extension unit or to the screed structure of an asphalt paving machine will serve to pull said body member into engagement with said other unit or said screed structure.
 2. The apparatus of claim 1 wherein said side walls and said bottom plate define two arcuate screed surfaces along opposite lower edges of the body member.
 3. The apparatus of claim 1 wherein said body member has a second open end, and tensioning member attachment means secured to and disposed inside of said body member adjacent said second open end.
 4. The apparatus of claim 3 wherein said attachment means includes a plurality of stud means extending from the body member toward the interior thereof, and said tensioning means comprise a plurality of closed loop members adapted to be positioned about the stud means of another similar extension unit.
 5. The apparatus of claim 3 wherein said tensioning means comprise a plurality of closed loop members having first ends disposed about said cam means and second ends connectable to the tensioning member attachment means of another extension unit.
 6. The apparatus of claim 4 wherein said body member includes a plate member pivotally secured to the exterior of said top wall near said first open end, and coupling means defined on said top wall near said second open end of said body member adapted for connection to the said plate member of another extension unit.
 7. The apparatus of claim 1 wherein the upper ends of said shafts extend through and terminate above said top wall.
 8. An extension unit for the screed of an asphalt paving machine comprising in combination: a body member having a hollow interior, first and second open ends, and including a substantially flat bottom plate; first and second shafts extending across the interior of said body member adjacent said first open end and including means supporting said shafts for rotation; first cam means secured to said first shaft and located inside said body member; second cam means secured to said second shaft and located inside said body member; first and second tensioning means respectively disposed about said first and second cam means and extending outwardly from said first open end of said body member and adapted to be moved toward the interior of said body member when said cam means are rotated; tensioning member attachment means secured to and disposed inside said body member adjacent said second open end, said attachment means including a plurality of stud means extending from the body member toward the interior thereof, said tensioning means comprising a plurality of closed loop members adapted to be positioned about the stud means of another extension unit, said closed loop members being steel rings having first ends disposed about said cam means with a curvature matching said cam means and second ends with a curvature matching the curvature of said stud means, whereby said tensioning means when coupled to another extension unit or an asphalt paving machine will serve to pull said body member into engagement with said other unit or the machine.
 9. An extension unit for the screed of an asphalt paving machine comprising in combination: a body member having a hollow interior, at least one open end, and including a substantially flat bottom plate; first and second shafts extending across the interior of said body member adjacent said open end and including means supporting said shafts for rotation; first cam means secured to saiD first shaft and located inside said body member; second cam means secured to said second shaft and located inside said body member; first and second tensioning means respectively disposed about said first and second cam means and extending outwardly from said open end of said body member and adapted to be moved toward the interior of said body member when said cam means are rotated; lock means coupled with said shafts for selectively locking said shaft against rotation when said tensioning means have been pulled to the innermost position thereof with respect to said body member, whereby said tensioning means when coupled to another extension unit or an asphalt paving machine will serve to pull said body member into engagement with said other unit or the machine.
 10. An extension unit for the screed of an asphalt paving machine comprising in combination: a body member having a hollow interior, at least one open end, and including an upper and a lower member each having a substantially flat section respectively defining the top and bottom of the body member and each having side wall sections extending substantially perpendicular from the respective top and bottom of the body member and means interconnecting said upper and lower members to define said body member; first and second shafts extending across the interior of said body member adjacent said open end and including means supporting said shafts for rotation; first cam means secured to said first shaft and located inside said body member; second cam means secured to said second shaft and located inside said body member; first and second tensioning means respectively disposed about said first and second cam means and extending outwardly from said open end of said body member and adapted to be moved toward the interior of said body member when said cam means are rotated; a first plurality of stud means extending downwardly from said top of said body member; a second plurality of studs extending upwardly from said bottom of said body member; said tensioning means comprising elongated members having a first end coupled with said cam means and a second end connectable to the studs of another unit, whereby said tensioning means when coupled to another extension unit or an asphalt paving machine will serve to pull said body member into engagement with said other unit or machine.
 11. The apparatus of claim 10 wherein said cam means comprises first and second substantially cylindrical cam members secured to said first shaft; third and fourth substantially cylindrical cam members secured to said second shaft; and said elongated members are each in the form of closed loop members having arcuate end sections.
 12. A screed extension unit for an asphalt paving machine comprising an elongated body member having first and second open ends, a hollow interior, and a flat bottom; a plurality of stationary connection members secured to the walls of said body member near the first end thereof; a plurality of movable connection members; means supporting said movable connection members near said second open end and including means for extending and retracting said movable members in a direction parallel to the longitudinal axis of the body member, said means for extending and retracting comprising first and second shafts extending through the interior of the body member and each having a plurality of cam means secured thereto and engaged with said movable members and said movable members having means engageable with the stationary members of another extension unit to thereby interconnect two adjacent units and cause the same to be pulled together when said movable members are moved from their extended to their retracted positions; first and second bottom adjustment means secured to said flat bottom of said body member adjacent said first open end and each having an end portion extending beyond the edge of said first open end; first and second threaded members extending respectively through said end portions and perpendicular to said Bottom; third and fourth bottom adjustment means secured to said flat bottom of said body member adjacent said second open end and each having an end portion extending beyond the edge of said second open end; and third and fourth threaded members extending respectively through said end portions of said third and fourth adjustment means and perpendicular to said bottom.
 13. The apparatus of claim 12 wherein said end portion of said third and fourth adjustment means are retractable to positions completely inside said body member. 